1. Field of the Invention
The present invention relates to an organic electroluminescence display device (hereinafter sometimes referred to as an organic EL display device). More particularly, the present invention relates to an organic EL display device in which an element substrate having a display region with organic EL elements being arranged therein is sealed with a concave translucent sealing substrate.
2. Description of the Related Art
An organic EL display device of this kind has a structure in which light emitted from the organic EL elements of the display region is irradiated on an observer side through the sealing substrate, which is a so-called top emission structure.
In such a structure, an organic light-emitting layer may be disposed above wirings used for driving control of respective pixels (wirings such as a scanning signal line and data signal line). Therefore, there is no fear of forming a light shielding region due to the wiring, thereby being capable of increasing an aperture ratio of the respective pixels, which is suited for attaining higher definition.
In an organic EL display device having such a structure, when moisture enters the display region with the organic EL elements being arranged therein, characteristics of the organic EL elements are sometimes degraded, and a so-called dark spot (non-light-emitting portion) occurs in the display region.
Therefore, generally, by applying a moisture absorbent (desiccant) for absorbing the moisture on the concave surface of the sealing substrate, and by sealing the element substrate with the sealing substrate, space around the display region is made to be a low moisture concentration atmosphere to prevent the entry of the moisture into the organic EL elements.
As such a structure, for example, there is known a structure in which the moisture absorbent is applied in a linear pattern to a region of the concave surface of the sealing substrate which does not overlap the display region of the element substrate, that is, to a region which is outside the display region, so as to surround the display region (see Japanese Patent Application Laid-open No. 2004-6286).
However, in the above-mentioned organic EL display device, the moisture absorbent is applied in a linear pattern so as to surround the display region, the amount of the moisture absorbent is limited, there are cases in which the characteristics of the organic EL elements can not be sufficiently stabilized.
The above-mentioned Japanese Patent Application Laid-open No. 2004-6286 discloses that a moisture absorbent in a linear pattern runs around the display region in a spiral manner, and is wound multiple turns so as to be spaced from one another. By increasing the number of the turns of the wound moisture absorbent, the amount of the moisture absorbent may be increased accordingly.
However, in this case, the width of the region where the moisture absorbent is formed outside the display region has to be large, and a so-called frame (a region between an outer periphery of the display region and an outer periphery of the element substrate) of the display device has to be large.
In other words, the technology disclosed in the above-mentioned Japanese Patent Application Laid-open No. 2004-6286 is inappropriate for a case where a large amount of a moisture absorbent has to be formed in a limited narrow region.